Swiss neutrality was essentially born out of the stinging defeat that the rampaging Swiss, having made it as far as Milan, suffered in 1515 against a combined French and Venetian force at Marignano, 16km southeast of Milan. After the bloody battle, the Swiss gave up their expansionist dream, withdrew from the international arena and declared neutrality for the first time. For centuries since, the country’s warrior spirit has been channelled solely into mercenary activity – a tradition that continues today in the Swiss Guard that protects the pope at the Vatican.
When the religious Thirty Years' War (1618–48) broke out in Europe, Switzerland’s neutrality and diversity combined to give it some protection. The Protestant Reformation led by preachers Huldrych Zwingli and Jean Calvin made some inroads in Zürich and Geneva, while Central Switzerland (Zentralschweiz) remained Catholic. Such was the internal division that the Swiss, unable to agree even among themselves as to which side to take in the Thirty Years' War, stuck to neutrality.
The French invaded Switzerland in 1798 and established the brief Helvetic Republic, but they were no more welcome than the Austrians before them, and internal fighting prompted Napoleon (then in power in France) to restore the former Confederation of Cantons in 1803 – the cantons of Aargau, St Gallen, Graubünden, Ticino, Thurgau and Vaud joined the confederation at this time.
Swiss neutrality as it exists today was formally established by the Congress of Vienna peace treaty in 1815 that, following Napoleon’s defeat by the British and Prussians at Waterloo, formally guaranteed Switzerland’s independence and neutrality for the first time. (The same treaty also added the cantons of Valais, Geneva and Neuchâtel to the Swiss bow.)
Despite some citizens’ pro-German sympathies, Switzerland’s only involvement in WWI lay in organising Red Cross units. After the war, Switzerland joined the League of Nations, but on a strictly financial and economic basis (which included providing its headquarters in Geneva) – it would have no military involvement.
WWII likewise saw Switzerland remain neutral, the country unscathed bar some accidental bombings on Schaffhausen in April 1944, when Allied pilots mistook the town in northeastern Switzerland for Germany, twice dropping bombs on its outskirts. Indeed, the most momentous event of WWII for the Swiss was when Henri Guisan, general of the civilian army, invited all top military personnel to Rütli Meadow (site of the 1291 Oath of Allegiance) to show the world how determined the Swiss were to defend their own soil.
The Swiss Constitution